Electrical connector with improved crosstalk compensation

ABSTRACT

An electrical connector with improved crosstalk compensation is disclosed. By including at least one coupling with a different frequency dependency than other couplings in the connector, crosstalk compensation performance is improved over a greater frequency range. The different frequency dependency may, for example, be used to compensate for phase shifts caused by distances between compensation circuitry and the plug/jack interface. Embodiments for decreasing these distances are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.11/464,335, filed on Aug. 14, 2006, which is a continuation of U.S.application Ser. No. 11/099,110, filed on Apr. 5,2005, which issued asU.S. Pat. No. 7,153,168, on Dec. 26, 2006 and which claims priority toU.S. application Ser. No. 60/559,846, filed on Apr. 6, 2004. All of theprevious applications are herein incorporated by reference in theirentireties.

FIELD OF THE INVENTION

The present invention relates generally to electrical connectors, andmore particularly, to a modular communication jack design with crosstalkcompensation that is less susceptible to propagation delay effects athigh frequencies.

BACKGROUND OF THE INVENTION

In the communications industry, as data transmission rates have steadilyincreased, crosstalk due to capacitive and inductive couplings among theclosely spaced parallel conductors within the jack and/or plug hasbecome increasingly problematic. Modular connectors with improvedcrosstalk performance have been designed to meet the increasinglydemanding standards. Many of these improved connectors have includedconcepts disclosed in U.S. Pat. No. 5,997,358, the entirety of which isincorporated by reference herein. In particular, recent connectors haveintroduced predetermined amounts of crosstalk compensation to canceloffending near end crosstalk (NEXT). Two or more stages of compensationare used to account for phase shifts from propagation delay resultingfrom the distance between the compensation zone and the plug/jackinterface. As a result, the magnitude and phase of the offendingcrosstalk is offset by the compensation, which, in aggregate, has anequal magnitude, but opposite phase.

Recent transmission rates, including those in excess of 500 MHz, haveexceeded the capabilities of the techniques disclosed in the '358patent. Thus, improved compensation techniques are needed.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an exploded perspective view of a communications connector,including a plug and jack;

FIG. 2 is a simplified schematic diagram illustrating parts of aconnector assembly that are primarily responsible for causing andcompensating for near end crosstalk;

FIG. 3 is a schematic vector diagram illustrating vectors A, B, and C ona time axis;

FIG. 4 is a schematic vector diagram illustrating magnitude and phasecomponents for vectors A, B, and C on a polar axis, with reference tocrosstalk vector A.

FIG. 5 is a schematic vector diagram illustrating vectors A, B, and C ona polar axis, with reference to compensation vector B;

FIGS. 6A-6C are schematic vector polar diagrams illustrating the effecton |A+C| relative to |B| as frequency increases for a typicalcommunications connector;

FIG. 7 is a graph of near end crosstalk versus frequency, illustratingcrosstalk performance of a typical Cat. 6 communications connector inrelation to TIA-568B requirements;

FIGS. 8A-8C are schematic vector polar diagrams illustrating the effecton |A+C+D| relative to |B| as frequency increases, for a communicationsconnector employing an embodiment of the invention;

FIGS. 9A-9C are schematic vector polar diagrams illustrating the effecton |A+C| relative to |B| as frequency increases, for a communicationsconnector employing an embodiment of the invention;

FIGS. 10A-10C are schematic vector polar diagrams illustrating theeffect on |A+C| relative to |B| as frequency increases, for acommunications connector employing an embodiment of the invention;

FIGS. 11A-11C are schematic diagrams, including equivalent circuitrepresentations, illustrating a first embodiment of the invention;

FIG. 12 is a schematic diagram illustrating an alternativeimplementation of the first embodiment shown in FIGS. 11A-11C;

FIGS. 13A-13C are simplified schematic diagrams illustrating aback-rotated contact design, a front-rotated contact design, and acorresponding equivalent circuit representation illustrating anembodiment of the invention;

FIGS. 14A and 14B are partial perspective view diagrams illustratingfront-rotated and back-rotated contact designs, respectively, inaccordance with an embodiment of the invention;

FIG. 14C is a partial perspective view diagram illustrating analternative front-rotated design in accordance with an embodiment of theinvention;

FIG. 15 a graph of near end crosstalk versus frequency, illustratingcrosstalk performance of a communications connector according to anembodiment of the invention, in relation to TIA-568B requirements;

FIG. 16 is a right-side view illustrating a front-rotated contactconfiguration in a communications jack, in accordance with an embodimentof the invention;

FIG. 17 is a right-side view illustrating a front-rotated contactconfiguration in a communications jack, in accordance with anotherembodiment of the invention;

FIG. 18 is an upper right-side exploded perspective view of a connectorjack in accordance with an embodiment of the present invention;

FIG. 19 is an upper right-side perspective view of a six-positionflexible PCB in accordance with an embodiment of the invention;

FIG. 20 is an upper right-side perspective view of a front sled withplug interface contacts and an upward-folded flexible PCB in accordancewith an embodiment of the invention;

FIG. 21 is an upper right-side perspective view of a front sled withplug interface contacts and a downward-folded flexible PCB in accordancewith an embodiment of the invention;

FIG. 22 is a partial upper right-side perspective view illustrating anupward-folded flexible PCB attached to plug interface contacts inaccordance with an embodiment of the invention;

FIG. 23 is a simplified right-side cross-sectional view of a portion ofa communications connector showing arrangement of an upward-foldedflexible PCB;

FIG. 24 is a simplified right-side cross-sectional view of a portion ofa communications connector showing arrangement of a downward-foldedflexible PCB;

FIG. 24A is a simplified right-side cross-sectional view of a portion ofa communications connector showing an alternative arrangement of aflexible PCB;

FIG. 25A is an upper right-side perspective view of one embodiment of aflexible PCB that may be utilized in accordance with the presentinvention;

FIG. 25B is a side view of one embodiment of a flexible PCB that may beutilized in accordance with the present invention;

FIG. 25C is a front elevational view of one embodiment of a flexible PCBthat may be utilized in accordance with the present invention;

FIG. 25D is a front elevational view of a flexible PCB with the fingersin an unbent configuration, for ease of illustration, in accordance withan embodiment of the present invention;

FIG. 25E is a cross-sectional view of the capacitive plates and leads ina flexible PCB in accordance with an embodiment of the presentinvention;

FIG. 25F is a front view of a first lead and capacitive plate in aflexible PCB with the fingers in an unbent configuration, in accordancewith an embodiment of the present invention;

FIG. 25G is a front view of a second lead and capacitive plate in aflexible PCB with the fingers in an unbent configuration, in accordancewith an embodiment of the present invention;

FIG. 25H is a front view of a third lead and capacitive plate in aflexible PCB with the fingers in an unbent configuration, in accordancewith an embodiment of the present invention;

FIG. 25I is a front view of a fourth lead and capacitive plate in aflexible PCB with the fingers in an unbent configuration, in accordancewith an embodiment of the present invention;

FIG. 26 is an upper right-side exploded perspective view of a connectorjack employing a flexible PCB in accordance with an embodiment of theinvention;

FIG. 27 is an upper right-side perspective view of an assembled jack inaccordance with an embodiment of the invention;

FIG. 28 is an upper right-side perspective exploded view of a jack inaccordance with an embodiment of the invention;

FIG. 29 is an upper right-side perspective view of a plug interfacecontact sub-assembly and PCB designed to accommodate 8-position plugs or6-position plugs;

FIG. 30 is simplified pictorial representation of an attachment of aferrite material structure that serves as an inductor;

FIG. 31 is simplified pictorial representation of two traces altered toincrease coupling;

FIG. 32 is simplified pictorial representation of two sets of traces,one utilizing a magnetic coupler and the other utilizing magneticmaterial placed in through-holes;

FIG. 33 is simplified pictorial representation of two parallel traces onseparate layers of a PCB; and

FIG. 34 is simplified pictorial representation of traces on a PCB withan overlay of magnetic material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is an exploded perspective illustration of a communicationconnector 100 comprising a plug 102 and a jack 104, into which the plug102 may be inserted. The plug 102 terminates a length of twisted paircommunication cable (not shown), while the jack 104 may be connected toanother piece of twisted pair communication cable or punch-down block(neither of which is shown in FIG. 1)

As shown from left to right, the jack 104 includes a main housing 106and a bottom front sled 108 and top front sled 110 arranged to supporteight plug interface contacts 112. The plug interface contacts 112engage a PCB (Printed Circuit Board) 114 from the front viathrough-holes in the PCB 114. As illustrated, eight IDCs (InsulationDisplacement Contacts) 116 engage the PCB 114 from the rear viaadditional through-holes in the PCB 114. A rear housing 118 havingpassageways for the IDCs 116 serves to provide an interface to a twistedpair communication cable or punch-down block. The general connector 100illustrated in FIG. 1 serves as background for the following discussionof improvements that may be made to the connector 100 to improvecrosstalk performance.

The simplified schematic diagram of FIG. 2 conceptually illustratesparts of a connector assembly 300 that are primarily responsible forcausing near end crosstalk, as well as those that may be used tocompensate for near end crosstalk. The plug 302 and plug interfacecontacts 304 contribute respective capacitive and inductive crosstalkcomponents C_(plug)+L_(plug) and C_(contacts)+L_(contacts), which may beapproximated as a lumped crosstalk vector A (see FIG. 4). A compensationzone 306 on the PCB 308 provides crosstalk compensation to producecompensation vector B. To account for the phase shift of B with respectto A that will occur due to propagation delay, a near end crosstalk zone310 (shown opposite the PCB 308 from IDCs 312) may contribute someadditional crosstalk C to reduce the phase shift's effect on combinedcrosstalk.

FIG. 3 illustrates vectors A, B, and C on a time axis. Note that thecrosstalk vectors A and C are opposite in polarity from compensationvector B. The vectors' relative displacement along the time axis iscaused by the physical distance of the compensation zone 306 and thecrosstalk zone 310 from where the plug 302 meets the plug interfacecontacts 304 (causing propagation delays T₁ and T₂) and the relativepermittivity of the intervening conduction paths.

FIG. 4 illustrates vectors A, B, and C on a polar axis, whereindisplacement along the time axis of FIG. 3 has been translated to phaseshift with reference to crosstalk vector A. As frequency increases, thephase shift of B will grow toward A and that of C will grow inopposition to A. For relatively small phase shifts, combined crosstalkcan be minimized by designing the compensation zone and crosstalk zoneso that |B+C| is approximately equal to |A| at a desired null frequency.

For frequencies up to about 300 MHz, the multi-zone crosstalkcompensation technique illustrated in FIGS. 2-4 is suitable to complywith Cat. 6 (TIA-568B) requirements for near end crosstalk. At higherfrequencies, however, this technique is unsatisfactory. To illustrate,FIG. 5 shows vectors A, B, and C on a polar axis, but with reference tocompensation vector B. To minimize combined crosstalk, |B| should beselected to be close to |A+C|. However, as frequency increases, A and Cexperience larger phase shifts, evidenced by larger angles from verticalon the polar axis of FIG. 5. Because the cosines of these increasingangles will decrease, |A+C| will become considerably less than |B|,resulting in unsatisfactory connector performance. This effect isillustrated in FIGS. 6A-6C, where |A+C| becomes relatively smaller than|B| as frequency increases.

FIG. 7 shows combined crosstalk performance of a typical Cat. 6connector using the technique discussed with reference to FIGS. 2-6.Note the frequency at which the NEXT crosses the TIA-568B requirementslimit.

To improve the NEXT performance to be suitable beyond the frequenciesthat are feasible with the above technique, an additional couplinghaving a magnitude that grows disproportionate to frequency relative toa typical coupling may be included in the connector. Alternatively, oneof the existing couplings can be modified to have a magnitude thatvaries disproportionally relative to the other couplings. Past typicalconnector couplings have been capacitive or mutually inductive,resulting in a magnitude that is proportional to frequency(approximately 20 dB per decade). The relative magnitudes of thesetypical connector couplings have remained approximately the samethroughout various frequencies. By introducing a coupling that growsdisproportionally relative to other couplings, the compensation forphase shifts caused by propagation delay (see FIGS. 2-6C, above) willretard the growth of the combined crosstalk through higher frequencies.

FIGS. 8A-15 and their accompanying descriptions show alternativeimplementations of additional couplings having a magnitude that grows ata disproportionate rate relative to typical couplings, in response tofrequency. Other implementations may also be used without departing fromthe spirit and scope of the present invention. FIGS. 8A-10C are vectordiagrams showing desired coupling characteristics. The description ofFIGS. 8A-10C is followed by a discussion of alternative methods forachieving the desired coupling characteristics.

According to a first implementation, the additional coupling is a fourthcoupling, D, having a magnitude with a frequency dependency that isdifferent than that of A, B, and C. For example, at low frequencies, A,B, and C change at a rate of 20 dB per decade, while D could change at alower rate, such as approximately 5 dB per decade. Then, at higherfrequencies (such as those greater than a null frequency of interest), Dcould change at a higher rate (such as 30 dB per decade), while A, B,and C remain relatively constant at 20 dB per decade. By selecting|B|-|D| to be equal to |A|+|C| at the null frequency, the combinedcrosstalk is near zero at low frequency, as shown by FIG. 8A. FIG. 8Bshows that as frequency increases, the phase angles of A and C increase,resulting in smaller vertical magnitude components to offset |B|.However, the more rapidly growing |D| increases to compensate fordecreasing |A+C|. FIG. 8C illustrates this effect at an even higherrelative frequency.

In a second implementation, illustrated in FIGS. 9A-9C, compensationzone vector B is designed to have a magnitude with a frequencydependency that differs from that of A and C. For example, at lowfrequencies, if A and C change at a rate of 20 dB per decade, then Bcould be selected to vary at a lower rate, such as 15 dB per decade. Athigher frequencies (such as those greater than a null frequency ofinterest), B could negatively change at a higher rate (such as −30 dBper decade), while A, and C remain relatively constant at 20 dB perdecade. In contrast to the first implementation illustrated in FIGS.8A-8C, no additional coupling is needed in this second implementation.By selecting |B| to be close to |A|+|C| at the null frequency, thecombined crosstalk is near zero at low frequency. As frequencyincreases, |A| and |C| will grow disproportionately faster than |B|, sothat |B| will be close to |A+C| at increased frequencies (see FIGS. 9Band 9C).

In a third implementation, illustrated in FIGS. 10A-10C, couplings A andC are selected to have a greater magnitude dependence on frequency thanB at frequencies higher than the null frequency. For example, at lowfrequencies, A, B, and C could all change at a rate of 20 dB per decade.At high frequencies, however, A and C could be selected to vary at ahigher rate, such as 25 dB per decade, while B remains at approximately20 dB per decade. By selecting |B| to be close to |A|+|C| at the nullfrequency of interest, the combined crosstalk is near zero at lowfrequency. Due to the higher frequency dependencies of |A| and |C|, themore rapidly growing |A| and |C| can compensate for the decreasing |A+C|that would normally occur with increased phase angles caused by highfrequency operation. Thus, low combined crosstalk can be maintained overa wider frequency range, as shown in FIGS. 10A-10C. Of course, to vary Awould likely require a change to the plug itself, which may beunacceptable in some cases. However, changing even C alone would providesome benefit.

The three implementations described above are merely examples ofpossible implementations. The relative rates of change in magnitudegiven in dB per decade may vary from one application to the next,depending on the specific construction and materials of the connectorassembly. In addition, the concept of relative magnitude variation overfrequency may be applied to improve performance at frequencies otherthan at or around the null frequency. The null frequency was chosen forthe above examples because it serves as a good starting point for makingadjustments to improve high frequency operation. For currentcommunications applications, null frequencies are generally observedaround 100-250 MHz. Different connector designs will likely exhibitdifferent null frequencies.

In a preferred embodiment, the communication jack includes pluginterface contacts for making electrical contact with the plug contactsin a plug, where the plug interface contacts and plug contacts introducecrosstalk to the connector. The crosstalk has an associated firstfrequency dependency based on a frequency of a communication signalbeing communicated. The jack has at least two crosstalk compensationzones, with at least one of the crosstalk compensation zones including acoupling having an associated second frequency dependency thatsubstantially differs from the first frequency dependency associatedwith the plug interface contacts and plug contacts. The first frequencydependency is a magnitude change of approximately 20 dB per decade. Thesecond frequency dependency is a magnitude that changes fromapproximately 0 dB per decade at a first frequency to approximately 20dB per decade at a second frequency. In a second preferred embodiment,the second frequency dependency is a magnitude that changes fromapproximately 20 dB per decade at a first frequency to less than 20 dBper decade at a second frequency. Finally, in a third preferredembodiment, the second frequency dependency is a magnitude change of 20dB per decade, and the first frequency dependency is a magnitude thatchanges from approximately 20 dB per decade at a first frequency togreater than 25 dB per decade at a second frequency.

The adjustments to magnitude dependency on frequency may be made usingseveral alternative techniques. The following discussion sets forth fiveof these techniques; however, others may be used without departing fromthe spirit and scope of the present invention.

Coupling alternative #1: FIGS. 11A-11C illustrate an example of a firstembodiment, in which a capacitance is placed in series with amutual-inductive coupling. The mutual inductive coupling generates acurrent in the reverse direction of the current flowing through thecapacitor, as shown in FIG. 11A, self inductance equivalent circuit 11B,and impedance equivalent circuit 11C. At low frequencies, couplingthrough the capacitor is low; therefore, the reverse current generatedin the secondary side of the inductance is also low. With risingfrequency, coupling through the capacitor will rise, increasing thecurrent through the primary side of the inductor, thereby causing ahigher reverse current through the secondary side of the inductor. As aresult, coupling declines proportionally to frequency. In a preferredembodiment, the “balanced source” 1262 shown in FIG. 11A is pairs 3 and6, while the “balanced sink” 1264 is pairs 4 and 5. FIG. 12 shows analternative arrangement of this embodiment, with pairs 3-4 and 5-6illustrated on the left side.

FIGS. 13A-13C illustrate how coupling alternative #1 may be implementedin either a back-rotated plug contact design 1300 or a front-rotatedplug contact design 1302. An example showing the resulting couplings inthe case where compensation capacitance is implemented on an interfacePCB 1304 is illustrated in the simplified equivalent circuit 1306.

FIGS. 14A and 14B illustrate the location in a front-rotated design 1400and a back-rotated design 1406 where the capacitive couplings may belocated. In the front-rotated design 1400, the capacitance is placed inthe tip nose region 1404 in a way that avoids physical interference withthe plug 1402. In the back-rotated design 1406, the capacitance mayagain be located in the tip nose region 1410, which is on the oppositeside of the plug 1408 when compared to the front-rotated design. For theback-rotated design 1406, the capacitance may be placed above or belowthe contacts of the tip nose region 1410, so long as it does notphysically interfere with insertion of the plug 1408. The placementsshown in FIGS. 14A and 14B result in capacitive couplings C35 and C46(from pairs 3 and 5 and 4 and 6, respectively) and mutual inductivecouplings M43 and M56 (from pairs 4 and 3 and 5 and 6, respectively).

FIG. 14C illustrates another location in an alternative front-rotateddesign 1412, as schematically illustrated in FIG. 12, where thecouplings may be located. In the alternative front-rotated design 1412,the couplings are placed even closer to the point of electrical contactbetween the plug 1414 and the plug interface contacts 1416. This closerplacement results from locating the couplings on the opposite side ofthe plug interface contacts 1416 from the plug 1414. This is achieved bymoving the inductive compensation from the conductors seen in the TipNose 1404 of FIG. 14A into a PCB, such as the flexible PCB shown in FIG.24A. This results in reduced propagation delay and thus, reduced phaseshift, which in turn provides better crosstalk performance.

Coupling alternative #2: In a second alternative, the coupling takes theform of a capacitance that varies with frequency relative to othercouplings. One example of such a capacitance is a capacitor having adielectric with a permittivity that changes with frequency.

Coupling alternative #3: According to a third alternative, the couplingis mutually inductive with a relative frequency-dependent inductance.One example of such an inductance is an inductive element composed of aferrite material. Ferrites (e.g. compounds with iron oxide andnickel-zinc or manganese-zinc) typically exhibit permeabilities thatvary greatly as a function of frequency starting at frequencies ofaround 100 kHz to 1 GHz. For example, a mixture of iron oxide andnickel-zinc has an initial permeability ranging from 10 to 1,500 over arange of 1 MHz to 1 GHz.

Coupling alternative #4: In a fourth alternative, the coupling is acapacitance in series with one or more resistors that arefrequency-dependent. For example, a conductor or semiconductor resistorcan be constructed to take advantage of the skin-effect to increaseresistance at high frequencies.

Coupling alternative #5: According to a fifth alternative, a capacitanceis placed in series with a self-inductive coupling. Increased inductanceat higher frequencies will result in less coupling through thecapacitance.

FIG. 15 shows improved combined crosstalk performance of a typical Cat.6 connector that may be obtained using the inventive techniquesdiscussed above with reference to FIGS. 8A-14. Note that the frequencyat which the NEXT crosses the TIA-568B requirements limit is much higherthan in FIG. 7.

The high frequency effects described with reference to FIGS. 2-7, andthe need to implement the above solutions to achieve acceptablehigh-frequency operation, arise primarily from the physical distancebetween the plug interface contacts and first compensation. Bydecreasing this distance, better performance (i.e. less phase shift dueto propagation delay) may be attained at high frequencies. For example,moving the first compensation point to a point less than approximately0.200 inches from the plug/jack interface provides better crosstalkperformance. FIGS. 16-28 illustrate physical changes that may be made toa jack to shorten the distance between the plug interface contacts andfirst compensation. These changes may be made in lieu of, or incombination with, the techniques described above. Optimal crosstalkperformance will result from implementing the combination.

FIG. 16 is a right-side schematic diagram illustrating a front rotatedcontact configuration 1600, including a plurality of plug interfacecontacts 1602 disposed in a contact carrier and front sled 1604 and avertical interface PCB 1606 having a contact portion 1608 connected to acrosstalk compensation zone (not shown). Compared to typical pluginterface contacts, the plug interface contacts 1602 are longer so thatthey come into contact with the contact portion 1608 of the verticalinterface PCB 1606. As a result, the distance 1610 between the contactportion 1608 and the point at which contact is made between an insertedplug and the plug interface contacts 1602 is significantly smaller thanfor typical plug interface contacts, as can be seen by comparing thedistance 1610 to distance 1700 in FIG. 17. Because the improved designhas a shorter distance between the plug contact and the firstcompensation, propagation delay is lessened, resulting in a smallerphase shift. This, in turn, enables better crosstalk compensation andoperation at higher frequencies than would be possible without such adesign. It should be noted that FIG. 17 includes inductive couplingsshown generally at 1702, which assist in crosstalk compensation.

FIG. 18 is an upper right-side exploded perspective view of a connectorjack 1800 employing the above concept. The jack 1800 includes a bottomfront sled 1804 and a top front sled 1808, each mechanically attached toa plurality of plug interface contacts 1806. A first end 1810 of theplug interface contacts 1806 may be inserted into through-holes in aninterface PCB 1812, while a second end 1814 includes plug interfacecontact ends that are longer than for a typical jack to allow contactwith a compensation zone on the interface PCB 1812. The sub-assemblycomprising the bottom front sled 1804, plug interface contacts 806, topfront sled 1808, and interface PCB 1812 is then inserted into a housing1802. Also to be inserted into through-holes on the interface PCB 1812are a plurality of IDCs 1816. A rear sled 1820 is snapped into thehousing 1802. A wire containment cap 1818 is configured to accept afour-pair twisted-pair communication cable for connection to the IDCs1816 through the rear sled 1820. The wire containment cap 1818 may thenbe snapped onto the rear sled 1820, forming an integrated communicationjack assembly.

While the above technique uses an alternative conductor path between theplug interface contacts and the first compensation, a second techniqueconsists of placing the first compensation zone closer to the plugcontact point by attaching a flexible PCB to the plug interfacecontacts. As an example, pad capacitors could be etched onto theflexible PCB to provide capacitive crosstalk compensation, therebyimproving the electrical performance of the jack.

FIG. 19 shows a six-position flexible PCB 1900 having six fingers 1902that may be used to attach the flexible PCB 1900 to plug interfacecontacts 2000 carried in a front sled 2002, as shown in FIG. 20. While asix-position flexible PCB 1900 is shown, an eight-positionimplementation is also possible. A six-position design may be preferredto avoid damage to standard RJ-45 jacks when a six-position RJ-45 plugis inserted. A standard six-position RJ-45 plug has plastic thatprotrudes further than the six contacts, which may lead to excessivedisplacement of plug interface contacts in the jack. The six-positionflexible PCB 1900 allows plug interface contacts 1 and 8 to be displacedfurther than plug interface contacts 2 though 7. The flexible PCB 1900is preferably constructed of a layer of copper adhered to a polyester orpolyamide substrate. The copper can be removed (e.g. by etching) invarious configurations to create a crosstalk compensation zone. Thefingers 1902 of the flexible PCB 1900 may be attached to the pluginterface contacts 2000 in any of a number of ways. Attachmenttechniques may include ultrasonically welding or heat soldering, forexample.

FIGS. 21 and 22 are perspective illustrations showing that the flexiblePCB 1900 may be folded upward or downward. Other orientations andconfigurations are also possible. FIG. 22 also shows a suitable regionof the plug interface contacts 2000 for attaching the fingers 1902 tothe plug interface contacts 2000. Depending on the number of fingers1902, the flexible PCB 1900 will be attached to the appropriate contactsfor tuning.

FIGS. 23 and 24 are simplified right-side cross-sectional viewsillustrating that the flexible PCB 1900 may experience deflection upward(FIG. 23) or downward (FIG. 24) in the jack as the plug interfacecontacts travel in response to insertion of a plug. As the plug isinserted into the jack, the flexible PCB 1900 follows the freedeflection of each contact regardless of whether or not it is attachedto the flexible PCB 1900. The fingers of the flexible PCB 1900 alsoaccommodate the natural variation in contact deflection due to variationin the plug contact termination height. Clearance may need to be builtinto the housing for the upward-deflecting flexible PCB 1900 of FIG. 23or into the front top sled for the downward-deflecting flexible PCB 1900of FIG. 24. Note that the vertically-spaced layout of plug interfacecontacts 2350 shown in FIGS. 23 and 24 advantageously providesadditional inductive crosstalk compensation. While this layout ispreferred, other layouts may alternatively be used.

FIG. 24A is a simplified right-side cross-sectional view illustrating analternative placement of the flexible PCB 1900 on the plug interfacecontacts 2350. In this alternative placement, which may, for exampleutilize the design shown in FIG. 14C, the flexible PCB 1900 and plug(not shown) are on opposite sides of the plug interface contacts 2350.This allows the couplings on the flexible PCB 1900 to be very close tothe plug contact point 2370, resulting in reduced propagation delay andthus, reduced phase shift. This, in turn, provides better crosstalkperformance. To allow for deflection of the plug interface contacts 2350when a plug is inserted, the flexible PCB 1900 may be designed to avoidcontact with other parts of the jack, such as the lower part of the pluginterface contacts 2350.

FIG. 25A is an upper right-side perspective view, FIG. 25B is a sideview, and FIG. 25C is a front elevational view of one embodiment of aflexible PCB 2400 that may be utilized in accordance with the presentinvention to provide crosstalk compensation. The PCB 2400 includes amain portion 2402 and attachment fingers, such as the finger 2404. Themain portion 2402 supports a plurality of capacitive plates (in thiscase, four plates, corresponding to plug interface contacts 3-6) toprovide capacitive coupling. As will be illustrated in FIGS. 25D-I, theleads to the capacitive plates provide an inductive coupling componentas well. The fingers 2404 serve as an attachment mechanism for attachingthe PCB 2400 to the plug interface contacts, using one of the schemesshown in FIGS. 23-24A, for example. While any suitable attachmenttechnique may be used, in the illustrated embodiment, a resistance weldrivet 2406 is used. In addition to attaching the PCB 2400 to the pluginterface contacts (or another conductor connected to the plug interfacecontacts), the rivet 2406 acts as a contact post for the capacitiveplates and their leads. This is illustrated in FIGS. 25B-I, which showfour layers of capacitive plates 2412 and leads (2408 a-d), throughwhich the rivet 2406 protrudes to make appropriate contact in thefingers 2404.

FIG. 25D is a front elevational view of the PCB 2400 with the fingers inan unbent configuration, for ease of illustration. FIG. 25E is across-sectional view of the capacitive plates and leads as viewed upwardfrom the bottom of the PCB 2400 toward line A/A in FIG. 25D. Note thatFIG. 25E does not show portions of the PCB 2400 that merely support thecapacitive plates and leads or serve as a dielectric or insulator. FIGS.25D-I show how the capacitive plates and leads are placed with respectto one another to result in a relatively high density of inductivecoupling in a relatively short distance. For example, in FIG. 25D, thecapacitive plate 2412 a and lead 2408 a for conductor 5 is the topmostplate and lead shown, having a sideways “U” shape. The same “U” shape,but with varying orientation, is used for conductors 3, 4, and 6, asshown by the dashed and solid lines of FIG. 25D. The physical placementand overlapping area of the capacitive plates determines the amount ofcapacitive coupling. Similarly, the separation of the leads from oneanother and the length of overlap determine the amount of inductivecoupling. FIG. 25E also illustrates the relative direction of currentflow in the respective leads, which provides a high density of inductivecoupling. FIGS. 25F-251 show, respectively, leads 2408 a-d andcapacitive plates 2412 a-d associated with, respectively, fifth, third,sixth, and fourth conductors of an eight-conductor jack.

FIG. 26 is an upper right-side exploded perspective view of a connectorjack 2500 employing the flexible PCB concept. The jack 2500 includes abottom front sled 2504 and a top front sled 2508, each mechanicallyattached to a plurality of plug interface contacts 2506. A first end2510 of the plug interface contacts 2506 may be inserted intothrough-holes in an interface PCB 2512, while a second end 2514 isattached to a flexible PCB 2516 that provides crosstalk compensation.The sub-assembly comprising the bottom front sled 2504, plug interfacecontacts 2506, top front sled 2508, interface PCB 2512, and flexible PCB2516 is then inserted into a housing 2502. Also to be inserted intothrough-holes on the interface PCB 2512 are a plurality of IDCs 2518. Arear sled 2520 is snapped into the housing 2502. A wire containment cap2522 is configured to accept a four-pair twisted-pair communicationcable (not shown) for connection to the IDCs 2518 through the rear sled2520. The wire containment cap 2522 may then be snapped onto the rearsled 2520, forming an integrated communication jack assembly.

While FIGS. 19-26 are described with reference to a flexible PCB, thisis merely one embodiment, and other embodiment using rigid PCBs or othercompensation schemes may also be possible without departing from theintended scope of the invention. A flexible PCB may assist in meetingmechanical constraints that may exist in some connector designs.

Another technique for shortening the distance between the crosstalkcompensation zone and the interface between the plug and plug interfacecontacts will now be described with reference to FIGS. 27-29. In thisthird technique, a back-rotated plug interface contact design is used inconjunction with an underlying compensation PCB to provide crosstalkcompensation extremely close to the interface between the plug and pluginterface contacts. As a result, propagation delays are minimized, as isthe phase shift of the crosstalk compensation. This simplifies theoverall compensation scheme by reducing the number of zones of crosstalkand compensation, which allows for better operation at high frequencies.

FIG. 27 is an upper right-side perspective view of an assembled jack2600. The jack 2600 includes a housing 2602 designed to accept a plug(not shown), a rear sled 2604, and a wire containment cap 2606configured to accept a communication cable (not shown). The housing2602, rear sled 2604, and wire containment cap 2606 latch together toform the assembled jack 2600.

FIG. 28 is an upper right-side perspective exploded view of the jack2600. In addition to the housing 2602, rear sled 2604, and wirecontainment cap 2606 described with reference to FIG. 27, the jack 2600includes a PCB support 2708 designed to support a compensation PCB 2710and an interface PCB 2712. A plurality of plug interface contacts 2714have first ends 2716 pressed into through-holes in the interface PCB2712 and second ends 2718, at least some of which slide along thecompensation PCB 2710 as a plug is received into the jack 2600. Aplurality of IDCs 2720 are inserted in through-holes in the interfacePCB 2712. FIG. 29 shows a closer perspective view of this plug interfacecontact sub-assembly (with the exception of IDCs 2720), which isinserted into the housing 2602, prior to the rear sled 2604 beingsnapped onto the housing 2602. Assembly of the jack 2600 furtherincludes positioning and installing a communication cable in the wirecontainment cap 2606, which is then snapped onto the rear sled 2604.

The plug interface contact sub-assembly (without IDCs 2720) shown inFIG. 29 is designed to accommodate either 8-position plugs or 6-positionplugs. When an 8-position plug is inserted into the jack, a downwardforce causes contacts 2 through 7 to slide along the compensation PCB2710. Contacts 1 and 8 deflect, but don't slide along the compensationPCB 2710. In contrast, when a 6-position plug is inserted into the jack,contacts 2 through 7 still slide along the compensation PCB 2710.However, contacts 1 and 8 deflect more than contacts 2 through 7, due toadditional plastic material on the 6-position plug. The clearance overthe compensation PCB 2710 provided by plug interface contacts 1 and 8allows for this additional deflection, while maintaining adequate normalforce between the plug and plug interface contacts 2714.

Inductance Enhancement for Compensation Circuits

The compensation circuits described above with reference to FIGS.11A-14C may be realized using standard layout and processing techniquescomposed of well-known electrical components. Additionally, generatingmutual inductance circuits with substantial inductive properties to actas these compensators is relatively simple, when limits are not placedon the trace length of the circuit. However, the limited space providedby the PCB board attached to the plug interface contacts within the jackhousing requires novel processing techniques and devices in order tocreate optimal inductive properties in as short of a trace as possible.These techniques should allow phase delay to be effectively introducedinto the compensation circuitry despite the shortened trace lengthsrequired of limited PCB area.

One technique is to use magnetic ferrite materials to increase themutual inductance between two signal traces. The magnetic materialreacts strongly to the movement of electrical charges in a first signaltrace, which also generate a magnetic flux. This magnetic flux isexhibited in the orientation of magnetic poles with the magneticmaterial, which then influences the moving electrical charges associatedwith a second electrical trace. Essentially, the magnetic material actsas a medium by which the two signal traces can be magneto-electricallycoupled to a degree determined by the geometry and magnetic propertiesof the ferrous or magnetic material used. FIG. 30 shows an attachment ofa ferrite material structure 3000 that serves as external inductorelement for the two signal traces 3002 running through it. The corestructure may be in the shape of several arches with the traces passingbelow the structure. Alternatively, the structure may have a solidhalf-cylindrical shape, or may be in the form of several rectangulararches. The external magnetic core may be composed of powdered iron,iron, nickel, steel, or a composite of these metals. Alternatively, itmay be composed of another magnetic ferrite material withmagneto-electric inductive properties. The magnetic core may befabricated separately from the board, and may be soldered, glued, orsnapped into place at pre-fabricated sites on the PCB 3004. Attachingthis component may be performed at a different site than that of the PCBmanufacturer after PCB processing has been completed.

FIG. 31 shows another method that can be used to increase mutualinductance between signal traces. In the method shown, no externalcomponents are required to generate the inductive coupling between thetraces. Rather, the geometry of the traces themselves is altered tomaximize coupling between the two signals. In this example, one trace3100 is formed into a first winding 3102, while the second trace 3104 isformed into a second winding 3106. The two windings overlap by aspecified amount and geometry, allowing for an increased interactionbetween the two traces per trace length. Alternatively, different tracegeometries may be used in order to increase the inductive couplingbetween the signals, such as elliptical or rectangular spirals.

FIG. 32 illustrates two similar methods that may be used to increase themutual inductance between signal traces. Like the first methodpresented, the methods shown in FIG. 32 utilize magnetic core materialsto increase the inductive coupling between two signal traces. In onemethod, the coupling is achieved by placing a magnetic coupler 3200directly over two parallel traces 3202 and 3204. The magnetic materialmay be applied to the surface of the board 3206 using a variety oftechniques. For example, the material may be melted and deposited ontothe surface using a drop dispenser, it may be screened on, it may beadded using an immersion and etch process, it may be rolled on, or themagnetic materials may be added using a similar process that allows forthe patterned and localized deposition of material onto the surface ofthe circuit board.

In another method shown in FIG. 32, the magnetic coupling material maybe inserted into the PCB 3206 through fabricated holes 3208 in theboard. The holes 3208 may then be filled with magnetic material 3210using, for example, a screening process. Alternatively, the magneticmaterial 3210 may be press fit into the PCB. The holes 3208 may becircular with cylindrical magnetic plugs used to fill the vacancies.Alternatively, the holes may consist of a different geometry that allowsfor inductive coupling between the traces through the magnetic corematerial.

In both embodiments shown in FIG. 32, the magnetic material 3210 may beany magnetic ferrite material, such as those described above.Additionally, the magnetic components may ideally be incorporated intothe PCB manufacturing process. However, the addition of the magneticcouplers may also take place after the board has been created at adifferent site from the PCB manufacturer.

FIG. 33 illustrates a similar method to the embodiments shown in FIG.32. However, in this embodiment, the two signal traces 3300 and 3302 arelocated in parallel on separate layers within the PCB 3304. Holes 3306are drilled into the PCB 3304 next to the signal traces 3300 and 3302and are then filled with magnetic material. The signal traces 3300 and3302 may be laid out so that they wrap around the magnetic cores,thereby increasing the amount of coupling induced by the magneticmaterial. Alternatively, other layouts may be used that either increaseor decrease the amount of coupling, as required by the electricalspecifications of the circuit. Filling the holes 3306 with magnetic corematerial may be accomplished via a screening process. The creation ofthe PCB holes 3306 and subsequent filling with magnetic material may beaccomplished during the PCB manufacturing process, although suchprocessing may also take place following the creation of the board andat a different site from the PCB manufacturer.

Another method for increasing the mutual inductance between signaltraces is illustrated in FIG. 34. In this method, the signal traces 3400are fabricated onto PCB 3402 in the normal fashion. After the traces arecreated, an internal layer 3404 of magnetic core material is laid on topof the board followed by another capping layer of PCB material 3406. Asa result, a layer of magnetic material may be embedded within thecircuit board. Alternatively, the internal layer 3404 of magnetic corematerial may be patterned and selectively removed prior to theapplication of the capping PCB layer 3406. This would allow the magneticmaterial to be present only in specific areas where increased inductivecoupling is desired, and would also prevent inadvertent coupling betweenunrelated signal traces. The creation of this type of circuit would needto be performed at the PCB manufacturer site and may require additionalprocessing steps to incorporate the magnetic material into the board.

All of the above methods may be used to increase the inductive couplingper trace length in PCB manufactured circuits. These methods help torealize the crosstalk compensation circuits necessary for mitigatingpropagation delay effects at high frequencies in modular communicationjacks.

Many modifications and other embodiments of the invention will come tomind to one skilled in the art to which this invention pertains havingthe benefit of the teachings presented in the foregoing descriptions andthe associated drawings. Therefore, it is to be understood that theinvention is not to be limited to the specific embodiments disclosed andthat modifications and other embodiments are intended to be includedwithin the spirit and scope of the present invention. Although specificterms are employed herein, they are used in a generic and descriptivesense only and not for purposes of limitation.

1. An electrical connector that includes one or more printed circuitboards, the one or more printed circuit boards comprising: a pluralityof conductive traces; a first compensation structure which includes aninductor-capacitor combination providing a first crosstalk compensationsignal having a first magnitude to a first of the plurality ofconductive traces; and a second compensation structure providing asecond crosstalk compensation signal having a second magnitude to thefirst of the plurality of conductive traces, wherein a ratio of thefirst magnitude to the second magnitude varies with frequency.
 2. Theelectrical connector of claim 1, wherein the inductor-capacitorcombination includes a series inductor-capacitor combination, the seriesinductor-capacitor combination including an inductor and at least onecapacitor in series with the inductor.
 3. The electrical connector ofclaim 1, wherein the inductor-capacitor combination comprises aself-inductive coupling.
 4. The electrical connector of claim 2, whereinthe inductor-capacitor combination comprises a self-inductive coupling.5. The electrical connector of claim 1, wherein the inductor-capacitorcombination comprises a mutual inductive coupling.
 6. The electricalconnector of claim 5, wherein electrical currents flowing through twoconductors which provide the mutual inductive coupling flow in the samedirection.
 7. The electrical connector of claim 5, wherein electricalcurrents flowing through two conductors which provide the mutualinductive coupling flow in opposite directions.
 8. The electricalconnector of claim 2, wherein the inductor-capacitor combinationcomprises a mutual inductive coupling.
 9. The electrical connector ofclaim 8, wherein electrical currents flowing through two conductorswhich provide the mutual inductive coupling flow in the same direction.10. The electrical connector of claim 8, wherein electrical currentsflowing through two conductors which provide the mutual inductivecoupling flow in opposite directions.
 11. The electrical connector ofclaim 1, wherein the first crosstalk compensation signal increases inmagnitude with frequency at a lower rate in dB than the rate in dB thatthe second crosstalk compensation signal increases with frequency. 12.The electrical connector of claim 1, wherein the first crosstalkcompensation signal increases in magnitude with frequency at a higherrate in dB than the rate in dB that the second crosstalk compensationsignal increases with frequency.
 13. The electrical connector of claim2, wherein the first crosstalk compensation signal increases inmagnitude with frequency at a lower rate in dB than the rate in dB thatthe second crosstalk compensation signal increases with frequency. 14.The electrical connector of claim 2, wherein the first crosstalkcompensation signal increases in magnitude with frequency at a higherrate in dB than the rate in dB that the second crosstalk compensationsignal increases with frequency.
 15. The electrical connector of claim1, wherein the inductor-capacitor combination includes a capacitor andtwo or more mutual inductive couplings.
 16. The electrical connector ofclaim 1, wherein the inductor-capacitor combination includes a magneticferrite material configured to increase an inductance.
 17. Theelectrical connector of claim 3, wherein the inductor-capacitorcombination includes a magnetic ferrite material configured to increasean inductance.
 18. The electrical connector of claim 4, wherein theinductor-capacitor combination includes a magnetic ferrite materialconfigured to increase an inductance.
 19. The electrical connector ofclaim 1, wherein the inductor-capacitor combination includes at leastone spiral trace formed by one of the conductive traces.
 20. Theelectrical connector of claim 19, wherein the inductor-capacitorcombination includes overlapping spiral traces formed by a pair of theconductive traces.
 21. The electrical connector of claim 16, wherein themagnetic ferrite material is disposed on the printed circuit board overa parallel pair of the conductive traces, the parallel pair ofconductive traces formed on the same layer of the printed circuit board.22. The electrical connector of claim 16, wherein the magnetic ferritematerial extends through the printed circuit board adjacent to each of aparallel pair of the conductive traces, the parallel pair of conductivetraces formed on the same layer of the printed circuit board.
 23. Theelectrical connector of claim 16, wherein the magnetic ferrite materialextends through the printed circuit board adjacent to each of a parallelpair of the conductive traces, the parallel pair of conductive tracesformed on different layers of the printed circuit board, each of theparallel pair of the conductive traces wrapping around the magneticferrite material.
 24. The electrical connector of claim 16, wherein atleast one of the one or more printed circuit boards comprises a firstlayer containing the conductive traces, a second layer containing themagnetic ferrite material, and a third layer containing PCB material,the second layer disposed between the first and third layers, themagnetic ferrite material disposed over a parallel pair of theconductive traces.
 25. An electrical connector that includes one or moreprinted circuit boards, the one or more printed circuit boardscomprising: a plurality of conductive traces; a first compensationstructure which includes a mutually inductive coupling having afrequency-dependent inductance, the first compensation structureproviding a first crosstalk compensation signal having a first magnitudeto a first of the plurality of conductive traces; and a secondcompensation structure providing a second crosstalk compensation signalhaving a second magnitude to the first of the plurality of conductivetraces; wherein a ratio of the first magnitude to the second magnitudevaries with frequency.
 26. An electrical connector that includes one ormore printed circuit boards, the one or more printed circuit boardscomprising: a plurality of conductive traces; a first compensationstructure which includes a series capacitor-resistor combinationproviding a first crosstalk compensation signal having a first magnitudeto a first of the plurality of conductive traces, the seriescapacitor-resistor combination including a capacitor and one or morefrequency-dependent resistors; and a second compensation structureproviding a second crosstalk compensation signal having a secondmagnitude to the first of the plurality of conductive traces; wherein aratio of the first magnitude to the second magnitude varies withfrequency.
 27. A plug-jack combination comprising a jack and a plugcontaining plug contacts, the jack comprising: a plurality of pluginterface contacts in the jack, the plug contacts contacting the pluginterface contacts at plug/jack interfaces of the plug interfacecontacts when inserted into the jack; a compensation zone adjacent tothe plug interface contacts; and a crosstalk zone positioned fartherfrom the plug/jack interfaces than the compensation zone, wherein atleast one of the compensation or crosstalk zones contains at least twocompensation structures, a first compensation structure providing afirst compensation coupling having a first magnitude at any particularfrequency of normal operating frequencies of the jack and a secondcompensation structure providing a second compensation coupling having asecond magnitude at the same particular frequency, and wherein the ratioof the first magnitude to the second magnitude varies with frequency.28. The plug-jack combination of claim 27, wherein the magnitude of oneof the first or second compensation couplings is larger than themagnitude of the other of the first or second compensation coupling atany of the normal operating frequencies of the jack.
 29. The plug-jackcombination of claim 27, wherein at least one of the first or secondcompensation structures comprises an inductor-capacitor combination. 30.The plug-jack combination of claim 27, wherein the first and secondcompensation couplings have opposite polarity with respect to eachother, the polarity of the first compensation coupling providescompensation, the polarity of the second compensation coupling providescrosstalk, and the ratio of the second magnitude to the first magnitudeincreases with frequency.
 31. The plug-jack combination of claim 27,wherein the at least one of the compensation or crosstalk zones is thecompensation zone, the first magnitude is larger than the secondmagnitude, and the ratio of the second magnitude to the first magnitudeincreases with frequency.
 32. The plug-jack combination of claim 27,wherein the functions of the first and second compensation structuresare independent of each other.
 33. A plug-jack combination comprising ajack and a plug containing plug contacts, the jack comprising: aplurality of plug interface contacts in the jack, the plug contactscontacting the plug interface contacts at plug/jack interfaces of theplug interface contacts when inserted into the jack; a compensation zoneadjacent to the plug interface contacts and having two compensation zonepairs connected to two pairs of the plug interface contacts; and acrosstalk zone positioned farther from the plug/jack interfaces than thecompensation zone and having two crosstalk zone pairs connected to thetwo compensation zone pairs, wherein a first rate of coupling magnitudeincrease in dB between the two pairs of the plug interface contacts andbetween the plug contacts vs. frequency is relatively constant, a secondrate of coupling magnitude increase in dB between the two crosstalk zonepairs vs. frequency is relatively constant, and a third rate of couplingmagnitude increase in dB between the two compensation zone pairs vs.frequency is relatively lower than the first and second rates.
 34. Aplug-jack combination comprising a jack and a plug containing plugcontacts, the jack comprising: a plurality of plug interface contacts inthe jack, the plug contacts contacting the plug interface contacts atplug/jack interfaces of the plug interface contacts when inserted intothe jack; a compensation zone adjacent to the plug interface contactsand having two compensation zone pairs connected to two pairs of theplug interface contacts; and a crosstalk zone positioned farther fromthe plug/jack interfaces than the compensation zone and having twocrosstalk zone pairs connected to the two compensation zone pairs,wherein a first rate of coupling magnitude increase in dB between thetwo compensation zone pairs vs. frequency is relatively constant, and asecond rate of coupling magnitude increase in dB between the twocrosstalk zone pairs vs. frequency is relatively higher than the firstrate.
 35. A method for providing compensation in a plug-jack combinationcomprising a jack and a plug containing plug contacts, the methodcomprising: providing a plurality of plug interface contacts in thejack, the plug contacts contacting the plug interface contacts atplug/jack interfaces of the plug interface contacts when inserted intothe jack; and providing a compensation zone adjacent to the pluginterface contacts and a crosstalk zone positioned farther from theplug/jack interfaces than the compensation zone, at least one of thecompensation or crosstalk zones containing at least two compensationstructures, a first compensation structure providing a firstcompensation coupling having a first magnitude at any particularfrequency of normal operating frequencies of the jack and a secondcompensation structure providing a second compensation coupling having asecond magnitude at the same particular frequency, the ratio of thefirst magnitude to the second magnitude varying with frequency.
 36. Themethod of claim 35, wherein the magnitude of one of the first or secondcompensation couplings is larger than the magnitude of the other of thefirst or second compensation coupling at any of the normal operatingfrequencies of the jack.
 37. The method of claim 35, wherein at leastone of the first or second compensation structures comprises aninductor-capacitor combination.
 38. The method of claim 35, wherein thefirst and second compensation couplings have opposite polarity withrespect to each other, the polarity of the first compensation couplingprovides compensation, the polarity of the second compensation couplingprovides crosstalk, and the ratio of the second magnitude to the firstmagnitude increases with frequency.
 39. The method of claim 35, whereinthe at least one of the compensation or crosstalk zones is thecompensation zone, the first magnitude is larger than the secondmagnitude, and the ratio of the second magnitude to the first magnitudeincreases with frequency.
 40. The method of claim 35, wherein thefunction of each of the first and second compensation structures areindependent of each other.
 41. A method for providing compensation in anelectrical connector, the method comprising: providing a first crosstalkcompensation signal to a first of a plurality of conductive traces usingan inductor-capacitor combination in a first compensation structure in aprinted circuit board, the first crosstalk compensation signal having afirst magnitude at any particular frequency of normal operatingfrequencies of the connector; and providing a second crosstalkcompensation signal to the first of the plurality of conductive tracesusing a second compensation structure in the printed circuit board, thesecond crosstalk compensation signal having a second magnitude at thesame particular frequency, a ratio of the first magnitude to the secondmagnitude varying with frequency.